<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;padding:0;
        }
        .box{
            width: 300px;height: 300px;background: blue;position: absolute;
        }
    </style>
</head>
<body>
    <div class="box"></div>
</body>
<script src="../tool.js">
</script>
<script>
    var obox=document.querySelector(".box")
    drag(obox);
</script>

</html>